The Role Of Cxcr3in Antigen-Induced Airway Hyperresponsivensess Andinflammation Of Asthmatic Mice

Objective:Asthma is a chronic obstructive airway disease featuring eosinophilic airway inflammation, airway hyperesponssiveness(AHR) to bronchospasmogenic stimuli, mucus hypersecretion and unbalanced Th1/Th2immune responses.Cytokines and chemokines play a key role in orchestrating the chronic inflammation of asthma. CD8+T cells participate in airway hyperresponsiveness (AHR) and allergic pulmonary inflammation that are characteristics of asthma. CXCL10by binding to CXCR3expressed preferentially on activated CD8+T cells, attracts T cells homing to the lung. We studied the contribution and limitation of CXCR3to AHR and airway inflammation induced by ovalbumin (OVA) using CXCR3knockout (KO) mice.Methods:48wild type (WT) mile mice with a C57BL/6background and48CXCR3knockout (KO) mile mice were divided into four groups:normal control1(WT/SAL group,24C57BL/6WT mice), normal control2(KO/SAL,24C57BL/6KO mice), asthmatic1(WT/OVA group,24C57BL/6WT mice), asthmatic2(KO/OVA group,24C57BL/6KO mice) gourps. Mice of asthmatic gourps were given intraperitoneal injection on days0and14with50μg of OVA absorbed to2.25mg Alum (Pierce) in200μl of sterile saline. From day25, mice were challenged with10ml of1% aerosolized OVA each for20minutes on six consecutive days in a chamber using a PARI nebulizer. Sham mice received aluminum hydroxide and were exposed to0.9% NaCl solution alone using the same protocol. Mice were sacrificed24hours after the last aerosol challenge. Lung sections were stained with hematoxylin&eosin reagent and Periodic acid-Schiff reagent in the pathological analysis. Cells of bronchoalveolar lavage were subjected to flow cytometer using a FACScan. Total protein content in BAL fluid was assayed using the BCA Protein Assay Kit. The concentrations of IL-4, IFNγ, and CXCL10in BAL fluid weredetermined by ELISA kits. Total RNA was extracted from whole lung using guanidine isothiocyanate methods and reverse-transcribed to cDNA using Omniscript Reverse Transcriptase.Results:Tachypnea, dysphoria,pruritus of head-face and twitch of abdominal muscle appeared obviously in WT/OVA group In aerosol challenge. Compared with the WT controls, CXCR3KO mice showed less OVA-induced infiltration of inflammatory cells around airways,and less mucus production. CXCR3KO mice failed to develop significant AHR. Compared with similarly-treated CXCR3KO mice, OVA-sensitized and challenged WT mice showed the typical pathological characteristics of allergic pulmonary inflammation in Semiqualitative analysis of inflammation in the lung by histopathology sensitized and challenged WT mice developed significant increases in lung resistance in response to increasing doses of inhaled methacholine. They also demonstrated significantly fewer CD8+T and CD4+T cells in BAL fluid, lower levels of TNFα and IL-4in lung tissue measured by real-time RT-PCR and in BAL fluid by ELISA, with significant elevation of IFNγ mRNA and protein expression levels.Conclusions:We successfully reproduced a type of asthma model in OVA-sensitized mice, given intraperitoneal injection and aerosol challenged. In conclusion, our study shows that CXCR3regulates OVA-induced allergic airway inflammation via recruitment of CD8+T cells into the airways to trigger the release of proinflammatory cytokines including TNFα and IL-4and inhibit the production of antiinflammatory mediators exemplified by IFNγ. Our findings suggest that designing an inhibitor specially targeting CXCR3may be helpful for the treatment of asthma.